Radar systems



July 26 1960 H. .1. H. WASSELL RADAR SYSTEMS 1na1 Filed Feb. 28, 1955 Orig A NGR 33% QWQ\\ INVENTOR HA R01 0 dasme flaw/5 WA 564! z BY M m i A ORNEYS 3 the aerial 1 and direct mechanical coupling employed between them.

In the embodiment shown in the drawing, a rotating coil equipment has been illustrated, the rotating coils (6 and 11) being driven by the selsyn motors 3, 4, 9. This, however, is by no means a necessary arrangement and there are distinct advantages, from the point of view of accuracy, in driving the coils 11 of the flying spot tube 12, mechanically. The advantages are of practical importance due to the stringent accuracy requirements of any height finder system using a nodding aerial, for minutes of arc, in elevation, is equivalent to 800 feet at 100 nautical miles so that elevation should be known to better than 5 minutes of arc. It is, therefore, of practical advantage to dispense with the selsyn motors and mount the bulk of the equipment so that the coils can be driven directly through suitable gears from the nodding aerial.

Even, however, when every precaution is taken to ensure that the coils 11 follow the movements of the nodding aerial 1 with faithful precision there still remains a further difliculty. To be of value elevation must, of course, be known in relation to a horizontal reference plane and in the embodiments so far described elevation is only determined in relation to some portion of the aerial support structure. In practice, however, it is almost impossible to avoid some deflection of such a structure due to wind forces, or as it rotates in azimuth, so that it is almost impossible to obtain a true and constant horizontal reference plane by using a non-nodding part of the aerial structure to provide the same.

I claim:

1. A height displaying radar system comprising an aerial subject to scanning deflection in the zenithal plane, a first cathode ray tube, the cathode ray beam of the tube being subjected to linear deflection in dependence upon range, a mask marked with lines of constant height, the mask being subjected to scanning by the light spot of said first tube, said mask being maintained in fixed relationship with respect to the first cathode ray tube, means for subjecting the cathode ray beam of said first tube to a circular deflection in accordance with the angle of elevation of the aerial with respect to the horizontal and to the radial deflection coincident with a scanning deflection, a second cathode ray tube acting as a display tube, means for subjecting the cathode ray beam of the latter tube to simultaneous radial and circular deflection respectively in accordance with range and angle of elevation of the target echoes, and means for applying a control signal to said second tube, said means for subjecting the cathode ray beam of the latter tube including means for producing a display of the mask on said latter tube, said means for applying a control signal including means for expanding or oflE-setting the display of said latter tube.

2. A radar system as set forth in claim 1, in which deflection coils are provided for said first and second cathode ray tubes for producing said deflection and wherein drive means are provided for moving said deflection coils relative to their associated tube, in dependence 'upon the elevation of the aerial with respect to the horizontal,

whereby the desired circular deflection is thereby attained.

3. A radar system as set forth in claim 1, in which deflection coils are provided for said first and second cathode ray tubes for producing said deflection and wherein a selsyn control system is provided as a drive for moving said deflection coils and wherein "the aerial and the deflection coils of the first and second cathode ray tubes each have an associated selsyn unit, and control circuits extending from the unit associated with the aerial to the units associated with the deflection coils.

4. A radar system as set forth in claim 1, in which deflection coils are provided for said first and second cathode ray tubes for producing said deflection and wherein a mechanical coupling is provided as a drive between said aerial and the deflection coils associated with the first and second cathode ray tubes, whereby the deflection coils are moved in dependence upon the zenithal movement of the aerial.

5. A radar system as set forth in claim 1, wherein light produced by the beam of the first tube is applied via an optical system including said mask, to a photoelectric cell, whereby the output from cell is characteristic of the tube output after modulation by the constant height lines of the mask, and wherein the output of the cell is applied, via an amplifier, as modulation to the cathode ray beam of the second cathode ray tube.

6. A height displaying radar system comprising an aerial subject to scanning deflection in the zenithal plane, a first cathode ray tube, the cathode ray beam of the tube being subjected to linear scanning deflection, a mask marked with lines of constant height, the mask being subjected to scanning by the light spot of said first tube, said mask being movable in accordance with the angle of elevation of the aerial with respect to the horizontal, and wherein the cathode ray beam of the first tube is subjected to radial deflection only, whereby relative circular movement between the line produced by the linear deflection of said cathode ray beam and said mask is produced in accordance with the angle of elevation with respect to the horizontal of said aerial as said elevation thereof is varied so as to scan zenithally, a second cathode ray tube acting as a'display tube, means for subjecting the cathode ray beam of said second tube to simultaneous radial and circular deflection respectively in accordance with range and angle of elevation of the target, means for modulating the cathode ray beam of said second tube with signals derived by the scanning of said mask by the first tube, and control signal means for selectively controlling ,the image produced on said second tube to modify the combined image of said second tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,522,528 

